Cardiac Care Show – Episode 1: Mechanical CPR

Hello, and welcome to the Cardiac Care Show. I’m your host Tom Bouthillet. In today’s episode I’d like to talk about mechanical CPR, which is a frequent topic of conversation in the Resuscitation group on Facebook and the #FOAMed community on Twitter. Alongside tracheal intubation, response times, and fire-based EMS, this is one of the most controversial topics in prehospital medicine.

Let me preface this by saying that these are my opinions which are based on my review of the medical literature and my real life experiences using mechanical CPR at the system level, including post-event analysis of resuscitations in which mechanical CPR was used. We use the LUCAS device, and there are other devices out there like the AutoPulse or the Thumper.

I understand that others may have different opinions about mechanical CPR, and that’s fine with me. Take my views for what they are worth, and combine them with your own review of the medical literature, and your own real life experiences. One thing we can say unequivocally is that we owe it to our patients to measure outcomes, and to perform post-event reviews of our resuscitation attempts, so that we understand the impact of our interventions.

Expertly performed CPR with the appropriate rate, depth, and recoil is the bedrock of resuscitation, so we might think it stands to reason that mechanical CPR must be superior to manual CPR. After all, human beings are not machines, so there will always be variability when human beings perform CPR. That’s why we use mechanical CPR in animal labs. In addition, CPR in the back of a moving ambulance is potentially dangerous and it makes it difficult to maintain CPR quality.

So, mechanical CPR is a no-brainer, right? Well, not so fast.

When mechanical CPR has been studied it has not been shown to improve mortality. Why should this be the case? In the first place, saving victims of sudden cardiac arrest is not easy. High quality CPR is extremely important but it’s just one variable in the chain-of-survival. In addition, we can’t use mechanical CPR on children or bariatric patients. Even when we can use mechanical CPR, we have to start out with manual CPR and transition them to mechanical CPR.

This is important because too many EMS systems look at mechanical CPR as a way to avoid having to become experts in resuscitation or having to send additional resources to the scene. In some systems, once mechanical CPR is established, the patient is loaded for transport and the patient is taken to the hospital, with or without return of spontaneous circulation.

Some of you might say, “Hey, that’s great! That way the patient can receive ECMO and PCI!” Two points here. First, in most of these cases, the receiving hospital is not transitioning the patient to ECMO or PCI. Second, even when ECMO or PCI is available for patients who are still pulseless, it’s a huge disservice to our patients to forgo a conventional resuscitation attempt in favor of rushing them to the hospital, in situations where a conventional resuscitation attempt is likely to result in a return of spontaneous circulation.

Just because mechanical CPR is established does not mean that nothing can go wrong. The plunger can and often will move during transport. When the plunger is too low and to the right we can have no blood flow, as evidenced by an echo by Sam Ghali, MD on Twitter.

We see the same thing when the plunger is placed over the LVOT as evidenced by a video shared with me by Patrick Ockerse, MD, a colleague of Scott Youngquist, MD, the Medical Director for Salt Lake City Fire Department. It’s it’s absolutely imperative that pulses be confirmed after applying a mechanical CPR device, and that pulses be periodically reassessed. Let’s also not forget that these patients still require ventilation and they still require defibrillation!

High Performance CPR boils down to rate, depth, recoil, ventilation, and peri-shock pause. Getting these things to happen flawlessly is a real challenge, even with a highly trained team, without the added complexity of transitioning the patient to mechanical CPR, placing the patient on a gurney, rolling them down the sidewalk, and loading them in the back of the ambulance.

It’s true that there are communities like Minneapolis where select patients with refractory VF may receive extraordinary measures at hospitals like Hennepin or Minneapolis Heart and in some cases they are able to save patients who almost certainly would have died, but we have to be smart about patient selection, and there’s a lot we still don’t know about the timing of all this. So when we look at the epidemiology of sudden cardiac arrest, we shouldn’t get distracted from the basics of optimizing the chain-of-survival.

That means implementing best practices like High Performance CPR (HP-CPR) and Telecommunicator CPR (T-CPR). For patients with true refractory VF (notice I did not say recurrent VF) we should be doing things like trying a different shock vector or double sequential defibrillation as an alternative to prematurely transitioning patients to mechanical CPR and transporting them to the hospital without ROSC.

The take-home message is this. If you’re using mechanical CPR correctly, it’s twice the work and twice the responsibility. That’s because you still have to be highly skilled in manual CPR. You also have to be very good at transitioning patients to mechanical CPR. Having trained this extensively, I can assure you that transitioning real patients to mechanical CPR is a far greater challenge than transitioning a manikin to mechanical CPR.

This is the most important point I want to emphasize today.

It’s not enough to say, “we can apply mechanical CPR in less than 10 seconds” which is a claim I hear all the time. That has to be demonstrated on actual patients on an ongoing basis. Having reviewed many dozens of these cases using CODE-STAT, there are typically at least 2 pauses, and sometimes 3 (applying the back plate, applying the device, repositioning the plunger).

One tip I learned from Michael Levy, M.D. is to sit the patient up and position the back plate on the patient’s back, and then lower the patient down, with the back plate pressed against the patient’s back. This prevents the back plate from moving when the patient is positioned on top of the back plate, which is how most systems do it, so this should to some degree help to minimize the issue of having to reposition the plunger.

I’ve heard all sorts of ideas and watched several videos (here, here, here, here) explaining how to minimize application time, and that’s great. It’s something we do have to train, but it’s not as easy as it looks, it’s different for live patients, and the evidence suggests that we can’t rely on our perception as to how long it takes.

When this was first studied by Yost et al. in 2012, researchers discovered that the median application time was 32.5 seconds. Importantly, provider estimates of pause length were often half the actual pause length. In other words, when providers were surveyed, they might say that it only took 15 seconds to apply the LUCAS device when in fact it took 30 seconds. So, the idea that you simply “slap on a LUCAS device” is dangerous. It reminds me of those who say, “Hey just drop a tracheal tube.” The subtext is that it’s so easy a child could do it and that simply isn’t the case.

When Michael Levy, MD and Dana Yost looked at this issue again in 2015, they showed that a QI initiative was successful in reducing the application time, defined as “last manual compression to first mechanical compression,” from 21 seconds to 7 seconds. This study did not report the total number of pauses, so we don’t know how often the plunger had to be re-positioned, but it does show both the necessity and the value of ongoing QA/QI practices when using mechanical CPR.

It’s not enough to “feel” like you’re doing a good job. I travel around the country quite a bit, and I’m intensely interested in resuscitation, so I ask a lot of people why they like mechanical CPR, and most of the time, I hear things like, “it frees up a set of hands” or “mechanical CPR is so effective that it’s not uncommon for our patient’s to have near-normal blood pressures.”

Two things here. First, contrary to popular belief, it is possible to perform High Performance CPR with 2 people. It’s more difficult but it is possible, as shown in this video by the Seattle / King County Resuscitation Academy. So even if mechanical CPR “frees up a set of hands” it doesn’t necessarily mean that it’s a good idea to initiate mechanical CPR right away, prior to the first shock, or even prior to 2nd or 3rd shock. It’s freeing up a set of hands to do what? Start an IV and give epinephrine? Second, while it’s true that you will often see things near-normal ETCO2 and SpO2 when mechanical CPR is used, that’s not the end point that matters. The end point that matters is neurologically intact survival.

You’ve probably surmised by now that I am fairly skeptical when it comes to mechanical CPR, and I am skeptical about using mechanical CPR as a primary resuscitation strategy. In my own system, when we purchased a LUCAS device, it was actually disruptive, and not in a good way. It led to significant interruptions during what I call the “sweet spot” of the resuscitation, meaning the first 5 cycles. Not only did it disrupt chest compressions, it also tended to disrupt the timing of defibrillation attempts during the peri-application period, so there might be a 3, 4, or even 5 minutes interval between shocks instead of just 2 minutes.

Some you may think, “well that’s a training issue”, and so it is, but most EMS systems are not performing high quality post-event reviews, so they’re not looking at this data with a critical eye. Just because you don’t measure it in your system does not mean that it’s not happening. In addition, mechanical CPR took away from the message that EMTs own CPR, which had been very successful in improving teamwork and morale in my department. Suddenly, the Battalion Chief would arrive on scene with the device, and all of the attention would turn toward this machine.

That’s why I now ask my EMTs and paramedics not to apply the LUCAS device until after a minimum of 5 cycles of High Performance CPR, or the 10 minute mark. Again, we consider this the “sweet spot” of the resuscitation. Most of our patients, if they’re going to come back, achieve ROSC during this time period. If a patient is still in cardiac arrest after the 5th shock or 10 minute mark, we refer to these patient’s as non-responders to Pit Crew CPR. But if it’s a relatively young patient, with a lot of quality adjusted life years left, with a good story (i.e., witnessed collapse, bystander CPR, and initial shockable rhythm) then we’re in for the long haul.

It may make sense to transition these patients to mechanical CPR due to what I call “resuscitation entropy” or the tendency for things to move toward disorder. If teamwork starts to break down, CPR quality starts to suffer, or there are factors on scene suggesting that we need to consider transporting the patient, even though they are in cardiac arrest, then the team leader, using Crew Resource Management, will make that decision with team input.

Some may ask, “Why do you transport patients who are in cardiac arrest?” Well, guess what. I’m still waiting to see the EMS system that never transports patients in cardiac arrest. Sometimes it’s the family’s wish, or because we’re in a public place, or because there is a persistent ETCO2 > 25 mm Hg and the patient is occasionally gasping but we’re at the 40 minute mark. I don’t believe in show codes, and half-hearted resuscitation attempts are unethical. We’re either in or we’re out. I think it’s true that CPR quality suffers in the back of a moving ambulance, so we do transition to mechanical CPR on those occasions.

I know that some of you out there passionately believe in mechanical CPR, and that’s fine. Most of the evidence suggests that it’s not harmful. If you’re an EMS system like Hennepin EMS that uses the LUCAS device, tracks outcomes with the CARES registry, and can prove that you’re on par with some of the best EMS systems in the nation, you’re on solid ground. On the other hand, if you’re not measuring outcomes, regardless of what your primary CPR strategy might be, you’re simply not in a position to contribute to our body of knowledge in this area.

Got an opinion about mechanical CPR? Leave us a comment! If there’s a topic you’d like us to cover on the Cardiac Care Show you can email me directly at tbouthillet@ecgmedicaltraining.com or tweet with the hashtag #CardiacCareShow! Thanks for joining us. See you next time.

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Tom Bouthillet (@tbouthillet) is Editor-in-Chief of ECGMedicalTraining.com (@ECGTraining) and Fire Captain/Paramedic in South Carolina where he is the Emergency Cardiac Care Program Manager and the STEMI and CARES Site Coordinator of his fire department.